Apple has introduced a limit of two iPhone Duo units per customer to tackle scalpers after preorders opened around four days ago. Shipping dates reportedly slipped to January next year within seconds of preorders going live.

With demand exceeding available stock, scalpers often buy large quantities of popular products and resell them at inflated prices. The two unit limit has been confirmed in the US, UK, Japan and Spain, although Apple may apply it worldwide.

Some eBay listings are already offering the iPhone Duo for as much as $5,000.

This is not Apple’s first attempt to prevent scalping. The company has introduced similar restrictions several times in China and other Western markets for products such as MacBooks.

However, these restrictions are not impossible to bypass. Scalpers can work in groups and use multiple virtual credit cards, delivery addresses and email accounts to place additional orders.